German Patent 36 36 129, and corresponding U.S. Pat. No. 4,846,065, Mayrhofer et al, assigned to an associated company of the assignee of the present application, describe a form cylinder which has a cylinder sleeve with a surface from which printing is to be effected, which surface has heat insulating properties and, generally, is hydrophilic. The sleeve, applied for example over a core or shaft, or the form cylinder itself can be associated with an image or printing subject matter transfer unit, located within the printing machine, over which imaging or subject matter information can be transferred to the surface of the form cylinder, in the form of oleophilic surface elements. The image information, that is, the oleophilic surface elements can be erased so that the form cylinder can be re-imaged without removal from the printing machine, and a new printing subject matter or printing image can be applied thereto. The oleophilic regions are inked as usual in the printing machine, for example prior to transfer of the image information to a blanket or offset cylinder; dampening fluid is supplied from a customary dampener, for example by dampener application rollers and the like, or, for example, by a combination inker-dampening fluid application roller.
U.S. Pat. No. 4,967,663, Metcalf, describes an unengraved metering roll made of porous ceramic material for depositing measured amounts of liquid as a coating on a substrate, such as a metal can. The pores in the ceramic accept the ink and replace the engraved pattern previously used on the outer surface of the roll. Manufacture of such a porous ceramic cylinder is known, and the referenced U.S. Pat. No. 4,967,663, Metcalf, describes, in detail, how such a porous cylinder or roll can be made. The size and number of the pores is determined by organic fillers added to the ceramic mass. Upon firing the ceramic mass, the organic fillers burn off and what is left is a porous ceramic body. Suitable organic fillers or additives are, for example, walnut shell flour, sawdust, straw dust, fish oil or the like.
Another method to make porous ceramic bodies, in form of a ceramic lattice or skeleton, is described in German Patent 38 40 137, Burger et al. A plastic foam, for example a polyurethane foam, is dipped into a ceramic suspension. Upon firing of the ceramic, the plastic foam burns out, and what is left is a foam or porous ceramic. The dimensions of the pores, for example pore diameters or average diameters, between 3 and 100 micrometers can be obtained, and the relative sizes of the pores can be controlled. A porosity of between 2% and 90% is obtainable, in dependence on the control of the process and the initial foam substance.